NEW ORLEANS  Hurricane Katrina drained the New Orleans metropolitan area of almost 40% of its residents and left the region with a whiter, wealthier and older population, according to the first Census Bureau estimates since the devastating flooding.

The special survey released today shows the New Orleans area, made up of seven parishes, became 73% white in the months after the hurricane Aug. 29, up from about 59% before the storm. The black population dropped from about 37% to 22%. The median age increased by about four years, and the median annual income rose from $39,793 to $43,447.

"This confirms what some people thought: There was a selective out-migration of poorer minorities," says William Frey, a demographer with the Brookings Institution.

The survey provides only estimates and is not official. It looked at counties and parishes in four states affected most by Hurricanes Katrina and Rita.

In New Orleans, the Census report confirms what local officials have been saying for months: Katrina did more damage in lower-income, black neighborhoods, which has made it more difficult for those residents to return.

Katrina and the subsequent breaching of the levee system flooded 80% of New Orleans and swamped St. Bernard and Plaquemines parishes to the east. Areas that did not flood are repopulating, but vast stretches of the metro area remain virtually empty. The Louisiana Recovery Authority estimates about 200,000 homes were destroyed.

The city of New Orleans lost about 64% of its residents after the storm, going from 437,000 in July to 158,000 in January, the Census Bureau says.

New Orleans demographer Greg Rigamer says the city's population has risen to 200,000 since the Census survey. Like the wider seven-parish metro area, New Orleans has lost more blacks than whites, Rigamer says. The May 20 mayoral election showed the city to be about 55% black, Rigamer says, down from two-thirds.

Lisa Blumerman of the Census Bureau says the demographic changes include an increase in requests for food stamps "across the board" in storm-affected areas. "Louisiana alone saw a 14% increase," she says. "That's incredible growth and shows an increased need for government help."

Along the Mississippi Gulf Coast, where Katrina hit directly and swept away miles of coastal homes, the population has dwindled 17%, from 363,000 to 303,000. The black population rose from 17% to 28%, while the white population declined from 80% to 71%.

Many hurricane evacuees are living in Houston, according to the survey. Harris County, which includes Houston, has an additional 90,000 people, or a 2.5% increase. Baton Rouge, about 80 miles east of New Orleans, saw its population increase by 17,000 people, or 4%.